1. Field of the Invention
Embodiments of the present invention generally relate to the fabrication of integrated circuits. More particularly, embodiments of the present invention relate to a method for depositing organosilicate layers on a substrate.
2. Description of the Related Art
In the manufacture of integrated circuits, plasma processes are increasingly being used to replace thermal processes. Plasma processing provides several advantages over thermal processing. For example, plasma enhanced chemical vapor deposition (PECVD) allows deposition processes to be performed at substantially lower temperatures than the temperatures required in analogous thermal processes. This is advantageous for processes with stringent thermal budget demands, such as in very large scale or ultra-large scale integrated circuit (VLSI or ULSI) device fabrication.
However, one problem that has been encountered with plasma processing in integrated circuit fabrication is device damage that occurs as a result of exposure of a device to non-uniform plasma conditions, such as electric field gradients caused by changing process conditions. While the susceptibility or degree of device damage typically depends at least partially on the stage of device fabrication and the type of device, many types and stages of devices can experience plasma-induced damage (PID). For example, a substrate that has a barrier layer or dielectric layer deposited thereon is more susceptible to PID due to the accumulation of surface charge, and a buildup of potential gradients during processing. Furthermore, as the size of devices become smaller and the dielectric layers become increasingly thinner, devices are becoming increasingly susceptible to PID.
In order to further reduce the size of devices on integrated circuits, it has become necessary to use conductive materials having low resistivity and to use insulators having low dielectric constants (low-k) to reduce the capacitive coupling between adjacent metal lines. Methods to form low-k dielectric layers include PECVD of organosilicate precursor gases to form organosilicate dielectric layers, such as carbon doped silicon oxide films. One challenge in this area has been to develop a carbon doped silicon oxide dielectric film that has a low k value, but also exhibits desirable adhesion properties to the underlying substrate or adjacent dielectric diffusion barrier layer materials which include silicon, silicon dioxide, silicon carbide, silicon nitride, oxygen-doped silicon carbide, titanium, titanium nitride, tantalum, tantalum nitride, tungsten, aluminum, copper, and combinations thereof. Inadequate adhesion may result in delamination of the low-k dielectric layer from the underlying substrate and potential failure of the device. One approach to enhancing adhesion of carbon doped silicon oxide films is inserting a thin silicon oxide film between the carbon doped silicon oxide layer and the underlying barrier layer. However, the thin silicon oxide layer must be a minor portion of the combined dielectric film to retain significant reduction in dielectric constant. Furthermore, the deposition of a thin silicon oxide layer prior to deposition of a carbon doped silicon oxide layer substantially increases processing time unless the layers are deposited sequentially in the same chamber. Sequential deposition has resulted in plasma arcing when the deposition conditions are changed. The plasma arcing damages the substrate surface and effectively negates any advantage in depositing the thin silicon oxide film and the carbon doped silicon oxide layer in the same chamber.
Therefore, there is a need for a process for depositing an organosilicate dielectric layer exhibiting high adhesion strength to an underlying substrate without plasma arcing.